1-aminopropanediol-2,3, which is useful as a starting material for non-ionic X-ray contrast agents, is an industrially interesting product (for example, see Belgian Pat. No. 855,580), and the demand therefore recently has increased.
Hitherto, it has typically been produced by a reaction of glycidol with ammonia.
For example, a process for the preparation of 1-aminopropanediol-2,3-which comprises a reaction of glycidol with 25% aqueous ammonia and a final distillation under reduced pressure conditions to obtain the refined product, is disclosed in "Ber. Deutsche Chem Ges" Vol 32, pages 750-757, 1899 (L. Knorr et al).
Furthermore, a process for the preparation of 1-aminopropanediol-2,3 which comprises a reaction of glycerine-alpha-monochlorohydrin with 25% aqueous ammonia and a final distillation under reduced pressure conditions to obtain the refined product, is disclosed in "Journal of Organic Chemistry", Vol. 27, pages 2231-2233, 1962 (K. Baum et al).
Still further, Japanese Patent Examined Publication (Kokoku) No. 37,342/1990 (corresponding to U.S. Pat. No. 4,356,323), Japanese Patent Unexamined Publication (Kokai) No. 161357/1981 (corresponding to U.S. Pat. No. 4,360,697), and Japanese Patent Examined Publication (Kokoku) No. 37,343/1990 (corresponding to U.S. Pat. No. 4,358,615) teach that 1-aminopropanediol-2,3 can be effectively prepared by a reaction of glycidol with liquid ammonia under pressurized conditions.
The above described disclosures disclose only the yield of 1-aminopropanediol-2,3 and the reaction conditions, such as a molar ratio between starting materials, reaction temperatures, reaction pressures, the amount of water to be used together with liquid ammonia, etc.
However, it has been known that 2-aminopropanediol-1,3, which is an undesirable impure component, and which can not be reduced to less than 0.30% by weight by the prior techniques without an improvement, is by-produced, even though in a minor amount, in the preparation of 1-aminopropanediol-2,3.
Heretofore, commercially supplied 1-aminopropanediol-2,3 has contained from more than 0.30 to 0.50% or more (based on the weight of 1-aminopropanediol-2,3) of 2-aminopropanediol-1,3.
It is noted that 2-aminopropanediol-1,3 adversely affects the use described above, even though it is present in a relatively minor amount.
More specifically, for example, there has been a problem such as low yields of final product in the case that the non-ionic X-ray contrast agents are manufactured using 1-aminopropanediol-2,3 containing large amounts of 2-aminopropanediol-1,3.
Accordingly, it has been desired that 1-aminopropane-diol-2,3 containing small amounts of 2-aminopropanediol-1,3 would be developed.
As the result of the background described above, the present inventors have earnestly investigated to prepare a highly purified 1-aminopropanediol-2,3 containing small amounts of 2-aminopropanediol-1,3, which can be obtained by distilling with a distillation column having low pressure loss from a crude 1-aminopropanediol-2,3 containing more than 0.30% of 2-aminopropanediol-1,3 (based on the weight of 1-aminopropanediol-2,3).